1. Field of the Invention
This invention relates to an intake air amount control system for internal combustion engines, and more particularly to an intake air amount control system of this kind, which controls the amount of intake air supplied to the engine according to electric loads on a generator driven by the engine.
2. Prior Art
Conventionally, there has been used an intake air amount control system for internal combustion engines, as proposed e.g. by Japanese Laid-Open Patent Publication (Kokoku) No. 4-51659, which includes a solenoid valve arranged in a bypass passage connected to an intake pipe of the engine in a fashion bypassing a throttle valve arranged therein. The proposed system controls the amount of intake air supplied to the engine during idling thereof through feedback control of the opening of the solenoid valve by the use of a control amount, more specifically, an amount of electric current to be supplied to the solenoid valve, based on the difference between the actual engine rotational speed and a desired engine rotational speed. The control amount is corrected by the use of electric load-dependent correction terms determined based on operative states of electric loads on a generator driven by the engine, such as an air conditioner and a power steering system.
A catalyzer, which is generally employed in internal combustion engines for purifying exhaust gases emitted from the engine, does not become activated until a considerable time period elapses after the start of the engine when the engine is started in a cold state. To accelerate the activation of the catalyzer, there is conventionally employed an electrically-heated catalyzer which is electrically heated to become promptly activated.
In the conventional intake air amount control system, however, electric power supplied to the electrically-heated catalyzer by the generator driven by the engine is not taken into account. As a result, the engine rotational speed can become unstable or it takes a longer time period to attain a desired engine rotational speed when the electric power is supplied to the electrically-heated catalyzer. This hinders the temperature of the catalyzer from rising promptly and makes it impossible to obtain desired exhaust emission characteristics.